Process for hydrogenating aromatic compounds containing sulfur impurities

ABSTRACT

Process for hydrogenating aromatic compounds containing sulfur impurities by contacting the same, at a temperature in the range of from 200* to 450*C and under a pressure of from 10 to 200 Kg/cm2, in a first step, with a catalyst containing a desulfurizing element selected from the oxides and/or sulfides of molybdenum, tungsten, nickel and cobalt, and an iron oxide, deposited on an alumina carrier used in an amount of 0.25 to 4 times the iron oxide amount, and in a second step, with a metal hydrogenation catalyst.

United States Patent [191 Cosyns et al.

[ 1 Aug. 12, 1975 1 PROCESS FOR HYDROGENATING AROMATIC COMPOUNDS CONTAINING SULFUR IMPURITIES [75] Inventors: Jean Cosyns, Nanterre; Jean-Pierre Franck, Bougival; Jean-Francois Le Page, Ruei1-Malmaison. all of France [73] Assignee: lnstitut Francais du Petrole des Carburants et Lubrifiants, Rueil-Malmaison, France 22 Filed: Aug. 31, 1973 21 Appl. No.: 393,607

301 Foreign Application Priority Data Sept. 1, 1972 France 72.31209 [52] US Cl. 260/667; 208/143; 208/89 [51] Int. Cl. C07c 5/10 [58] Field of Search 260/667; 208/141, 143,

[56] References Cited UNITED STATES PATENTS 3,405,190 10/1968 Logemann et a1. 208/143 Primary ExaminerDelbert E. Gantz Assistant Examiner.luanita M. Nelson Attorney, Agent, or F irm--Millen, Raptes & White 57 ABSTRACT Process for hydrogenating aromatic compounds containing sulfur impurities by contacting the same, at a temperature in the range of from 200 to 450C and under a pressure of from 10 to 200 Kg/cm in a first step, with a catalyst containing a desulfurizing element selected from the oxides and/or sulfides of molybdenum, tungsten, nickel and cobalt, and an iron oxide,

deposited onan alumina carrier used in an amount of 0.25 to 4 times the iron oxide amount, and in a second step, with a metal hydrogenation catalyst.

14. Claims, No Drawings PROCESS FOR HYDROGENATING AROMATIC COMPOUNDS CONTAINING SULFUR IMPURITIES This invention concerns a process for hydrogenating aromatic compounds, particularly such aromatic compounds as benzene, alkylbenzenes, polycyclic aromatic hydrocarbons and their alkyl derivatives, alone or diluted in various petroleum cuts, in the presence of a composite catalyst system which has in particular the advantage of permitting the treatment of materials having high sulfur compound contents and of providing a product which is not only dearomatized but also desul furized.

An important application of this invention consists of hydrogenating aromatic compounds present in certain petroleum cuts such as white spirit, commonly used in various industries such as those of paint, rubber, solvents for use in agriculture etc.

Another application, which is not less important, is the hydrogenation of the aromatic hydrocarbons present in the kerosene cuts, used as fuel, in view of improving their smoke point; this empirical index is in fact proportional to the ratio of hydrogen to carbon in the considered hydrocarbon or cut. This ratio H/C is directly responsible for the combustion heat which is higher as the ratio I-I/C is greater, i.e. when the aromatic hydrocarbons have been more completely hydrogenated. This quality is specially required for such fuels as jet-fuels which have an always increasing demand (consumption in France of 850 000 metric tons in 1965, 1,500,000 metric tons in 1970, about 2,700,000 metric tons expected for 1975), the specification of such fuels with respect to the maximum content of aromatic compounds being liable to become more severe as the result of the increased use of supersonic transport.

The processes for hydrogenating aromatic hydrocarbons, as already known, may be classified into two categories which both have a certain number of disadvantages.

In the first category are the processes performed in a single stage, using catalysts comprising metals of the iron group (iron, cobalt, nickel) of the periodic classification of elements, associated with metals of group VI A. In these processes, the catalysts are active in the sulfurized state. The catalysts used in this category of processes, perform simultaneously the hydrodesulfurization of the feed charge and a certain hydrogenation of the aromatic compounds. However, in spite of the use of high hydrogen pressure and of high tempera ture (350C and 60 Kg/cm by way of example), the final contents of aromatic hydrocarbons are generally high 3 to 5% by volume as a minimum) and do not permit the production of sufficiently dearomatized sol-' vents. Moreover, in this type of process a certain amount of hydrocracking is always observed and requires subsequent fractionations which increase the cost of the process.

The second category of processes performed in two stages, makes use of catalysts comprising metals of group VIII acting in the metal state after reduction.

The catalysts generally, used are either based on nickel, or on noble metals such, for example, as platinum. The catalysts are particularly sensitive to the presence of sulfur compounds and/or hydrogen sulfide. It is accordingly necessary to desulfurize the charges and to remove H 8 before the hydrogenation step so that a charge whose sulfur content is generally smaller than 50 ppm (parts per million of parts) is contacted by the hydrogenation catalyst.

The removal of H 8, between the two stages, makes the process more complex. In the case of a flow sheet with a single hydrogen circuit, it is necessary to provide a device for washing the recycle gas; when it is desired to omit said washing of the gas, it is necessary in such a case, to have two independent recycle circuits. In both cases the process is complex and results in a high operating cost.

Some processes carried out with catalysts based on platinum are considered as adapted to the treatment of charges containing up to 300 ppm of sulfur. But, under these conditions, the content of residual aromatic hydrocarbons becomes quickly too high for making it possible to use the resulting product as solvent and, in addition, it becomes necessary to operate at higher temperatures in order to compensate for the loss of activity of the catalyst. Such a high temperature treaatment is thermodynamically unfavourable and is detrimental to the yield of the operation and to the cost of the process, since it produces,'as the processes of the first category, a certain amount of hydrocracking.

The process of the invention avoids these disadvantages.

As a matter of fact, it makes it possible to process petroleum cuts containing up to 1000 ppm of sulfur while producing cuts substantially entirely free of aromatics and containing substantially no sulfur (generally less than 1 ppm) with a yield by weight close to 100%;

The process consists of treating, in the presence of hydrogen, at a temperature of from 200to 450C, preferably from 250 to 350C, under a. pressure of from 10 to 200 Kglcm preferably from i 20 to Kg/cm at least one aromatic hydrocarbon in a reaction system comprising in successiveorder: first of all a hydrodesulfurization catalyst adapted to retain the hydrogen sulfide formed during the hydrodesulfurization reaction and then a hydrogenation catalyst, without intermediary fractionation. The treated material may consist for example of benzene, alkylbenzenes,

particularly toluene, xylenes, ethylben'zene, aromatic and alkylaromatic polynuclear hydrocarbons, separately or in admixture with one another, or diluted in petroleum cuts such as white spirit or kerosene, these hydrocarbon mixtures and/or cuts containing optionally up to 1000 ppm by weight of sulfur, and for example l to I000 ppm. I

The treated feedstocks generally have boiling points within the range of from 50 to 350C and may be obtained by straight run distillation of petroluem or by any other operation of refining and/or transformation of petroleum cuts. They may contain for example from 1 to substantially of aromatic hydrocarbons.

The catalyst used according to this invention for simultancously removing the sulfur compounds from the feedstock and retain the hydrogen sulfide formed during the dehydrodesulfurization reaction, comprises essentially:

a. at least one element active for hydrodesulfurization as known in the art, for example molybdenum and/or tungsten, with or without nickel and/or cobalt, and preferably cobalt-molybdenum, nickel molybdenum, cobalt-tungsten, nickel-tungsten etc. particularly in the form of oxides or.sulfides;

b. alumina;

, residue obtained in the manufacture of alumina, whose composition is substantially as follows:

Fe calculated as rep, 30 to 60 7c of dry weight Ti calculated as TiO 1 to 10 Si calculated as SiO: 5 to 20 Na calculated as Na CO 5 to 15 A1 calculated as A1 5 to 30 Miscellaneous 0 Mn O P 0 V 0 5 (for example CaO- The separation of the red mud is described for example in Kirk and Othmer Encyclopedia of Chemical technology, second edition, Vol 1 (1963) pages 937-9415 Ullmanns Encyklopaedie der technischen Chemie, third edition, Vol 3 (1953) pages 375385, Urban and Scharzenberg editors, Munich.

In the Bayer process for manufacturing alumina, bauxite is dissolved in a soda lye: the obtained sodium aluminatesolution is separated from an insoluble residue, called red mud. The red mud is then washed with waterfojr extracting soda and sodium aluminate therer m! As iron source there can be used an iron salt, for ex ample a nitrate, acetate, carbonate, sulfate or chloride, although this is less preferable.

The proportion of active elements, molybdenum, tungsten, cobalt and/or nickel oxides and/or sulfides in the catalyst, is generally from 2 to 40%, expressed by weight of vthejcorresponding metal. A preferred catalyst contains from 5 to 35% by weight of molybdenum and- /or tungsten and from 1 to by weight of nickel and- /or.-cobalt calculated as metal. The catalyst has a specificsurface generally from 50 to 400 m /g, preferably from 100 to 300 m /g.

. In some cases, the material containing iron oxide also contains alumina; it is the case of the red muds; however, these red muds generally do not permit, by themselves, to obtain a catalyst having the required specific surface, unless a certain proportion of conventional alumina such as, for example, an alumina gel, is added thereto.

,The so-composed catalyst is particularly interesting since it performs the hydrodesulfurization reaction over a relatively long period without formation of hydrogen sulfide in the gaseous and/or liquid effluents. in contrast to the use of conventional hydrodesulfurization catalysts, such as Co Mo, Ni M0 or Ni W supported on alumina, for example. This catalyst is also very-interesting in that it is easily regenerated by a mere treatment with steam, so that its use results in an economical and really continuous process.

The compounds of metals which are precursors of species active for hydrodesulfurization may be introduced into the catalyst either by mixing with the mixture alumina iron oxide or red muds or by impregnating of the mixture alumina-l-iron oxide or red muds preliminarily brought to the desired shape, for example by extrusion. For manufacturing the catalyst carrier, there will advantageously be used ratios of A1 0, to red muds, from 9 to 0.1 l by weight and preferably from 2.3 to 0.43 these values being not limitative.

Another technique consists of mixing, as homogeneously as possible, the particles, extrudates for example, of a conventional hydrodesulfurization catalyst with particles, e.g. extrudates, of iron oxide and/or red muds.

As hydrogenation catalysts, there can be used all those which are generally known as such, ie the metals of group VIII of the periodic classification of elements such as Ni, Co, Pt, Rh, Ru, Pd etc. incorporated to (or deposited on) any carrier such for example as alumina, silica, alumina-silica etc. These metals may be used alone or in association in the form of mixtures and/or alloys with one another or with an element from groups VI A or VII A such for example as: W, Mo, Re, The content of metal from group VIII is generally from 0.1 to 1.5% by weight of the catalyst.

The molybdenum, tungsten, nickel, cobalt or noble metal compounds which can be used for manufacturing the abovementioned catalysts need not to be listed here, since they are well-known in the art.

The two catalysts in the process of the invention may be used in different manners.

According to a first manner, the two catalysts may be catalysts are placed in two successive reactors which are traversed in successive order by the totality of the reactants.

In another alternative embodiment of the process,v

which is generally preferred, the absorbing hydrodesulfurizing catalyst is placed in two reactors branched in parallel and used alternatively, one being in regenera-' tion, while the other is in operation, the hydrogenation catalyst being placed in a third reactor following the hydrodesulfurization reactor in operation.

An important feature of the process described in the present invention, is that, irrespective of the retained flow sheet and of the use of a single reactor or successive reactors, there is still obtained an integrated system which does not require any intermediate treatment of the effluents (such as for example cooling, separation, gas expansion Moreover, the operating conditions are such that practically no hydrocracking occurs and therefore, it is unnecessary to provide for a fractionation system of the liquid product.

As far as the regeneration of the absorbing hydrodesulfurizing catalyst is concerned, it may be easily carried out by passing steam through the catalyst bed, for example at a temperature from to 600C and preferably from 350 to 450C, these values being not limitative. This treatment may be applied only to the absorbing-hydrodesulfurizing catalyst or to both catalysts used according to the invention. The steam may be either pure or diluted with inert gas; for example gas produced by the combustion of hydrocarbons may be convenient. A steam content of at least 10% in the regeneration gas is preferred.

This regeneration is appropriate as soon as there is observed the presence of a noticeable proportion of free H S in the effluent issuing from the first catalyst zone. During the regeneration, H S is liberated from the catalyst. The regeneration may be discontinued as soon as H S is no longer liberated in a noticeable amount.

The regeneration period is generally from minutes to 48 hours according to the selected steam flow rate.

This regeneration is advantageously followed by a scavenging with hydrogen so as to expel the residual hydrogen sulfide.

The usual conditions of p.p.h., i.e. of the hourly flow rate of feedstock by weight with respect to the catalyst weight, may be advantageously as follows:

On the absorbing hydrodesulfurizing catalyst, the p.p.h. will be advantageously from 0.2 to 10 and preferably from 0.5 to 5; the optimal p.p.h. depends on the sulfur content of the feedstock and of the ratio alumina/iron oxide of the catalyst; for example, for feedstock containing from 300 to 600 ppm of sulfur, treated over a catalyst having a ratio alumina/red muds of l, the p.p.h. values may be chosen in the range of from 0.5 to 2.

The selected p.p.h. over the hydrogenation catalyst depends on the desired aromatic hydrocarbons content of the hydrogenated product; it will generally be in the range of from 1 to and preferably from 5 to 15.

These usual values of the p.p.h. are given by way of mere illustration, it being understood that, in some particular cases, satisfactory results are obtained by using p.p.h. values outside the above-defined ranges.

The following examples illustrate the invention, but are not to be considered as limiting the scope thereof.

EXAMPLE 1 ln this example, three catalysts are prepared.

The first catalyst is a hydrodesulfurization catalyst containing cobalt oxide and molybdenum oxide in a proportion of 4.7% by weight of C00 and 13.6% by weight of M00;, admixed with an alumina gel. The incorporation of the metal oxides is carried out in a conventional manner, for example by mixing, in the presence of a small amount of water, the alumina gel with the desired proportion of cobalt nitrate and ammonium paramolybdate; the resulting paste is extruded and then calcined in air at about 550C so as to obtain the corresponding oxides of cobalt and molybdenum. Another equivalent method for incorporating the metal oxides consists of impregnating the alumina, preliminarily brought to the desired shape, by means of aqueous solutions of catalyst metals and then calcining as above in air at about 550C.

The second catalyst is a hydrogenation catalyst containing 0.3% by weight of platinum deposited on an alumina carrier. The deposit of platinum is carried out in a conventional manner by impregnating the carrier with an aqueous solution of hexachloroplatinic acid and then drying and calcining at about 550C.

The third catalyst is an absorbing hydrodesulfurization catalyst containing 4.7% by weight of cobalt oxide and 13.6% by weight of molybdenum oxide introduced by mixing cobalt nitrate and ammonium molybdate with an alumina-red mudmixture having a ratio alumina/red mud equal to 0.67, i.e. containing 40% by weight of alumina and 60% by weight of red muds; the

Ffigon 46.40 71 by weight Ti0 4.80 Si0 13.20

-2 m 10. 1 5 Ratio 2 17.57 A1 0 F620 1 8 b.w

Mn O 0.49 2 .1 0.09 P 0 0.39

' 93.09 93.09 H2O 6.20 miscell aneous 0.71

The characterizing features of the various solid catalysts used in this example can be summarized as follows:

Hydrodesulfurization catalyst HDS CATA.

Shape: extrudates having a 1.5 mm diameter Filling density: 0.69 g/cc Total pore volume: 0.545 cc/g Specific surface: 324 m /g (B.E.T. method) Hydrogenation catalyst (H. CATA.)

Shape: extrudates of a 1.5 mm diameter Filling density: 0.61 g/cc Total pore volume: 0.7 cc/g Specific'surface: 214 m /h (B.E.T. method) Absorbing hydrodesulfurizing catalyst (A.HDS.CATA.)

Shape: extrudates of 1.5 mm diameter Filling density: 0.73 g/cc Total pore volume: 0.546 cc/g Specific surface: 188 m /g (B.E.T. method) The feedstock subjected to hydrogenation consists of a petroleum cut from straight run distillation, of the white spirit type, having the following characteristics:

ASTM distillation range: l52l95C Specific gravity at 15C: 0.792

Aromatic content: 17.5% by volume Sulfur content (as present in sulfur compounds): 410

ppm by weight The desired final product is a solvent which does not contain more than 3% by volume of aromatic compounds.

The following three tests have been carried out:

1. In a first test the white-spirit is hydrogenated over the hydrogenation catalyst containing platinum (H. CATA.) in the following conditions:

Temperature: 300C Total pressure: 45 Kg/cm p.p.h.: 4

H /feed stock: 1.5 moles/mole 2. In the second test the same white-spirit is hydrogenated in a reactor containing two successive beds of catalyst: the first bed is formed from the hydrodesulfurization catalyst (HDS. CATA.) and the second bed from the platinum hydrogenation catalyst (H. CATA.

The conditions of pressure, temperature and ratio h j feedstock are the same as for the first test: for each of the two catalysts, taken separately, the p.p.h. is equal to 4.

3. In the third test, the same white-spirit is still hydro genated in a reactor containing a first bed of absorbing dehydrodesulfurizing catalyst (A.HDS.CATA.) followed with a second bed of platinum hydrogenation catalyst (H. CATA.).

The conditions of pressure, temperature and ratio H /feedstock are the same as in the preceding tests 1 and 2; the respective p.p.h. values being:

A.HDS.CATA. p.p.h. 1.35

H. CATA. p.p.h. 8

As shown in the following table I, the device although operating with a p.p.h. value of 8 over a platinum hydrogenation catalyst gives better results than the device of test 2 with a p.p.h. value of 4 (8/2) over the hydrogenation catalyst.

The results of these three tests are summarized in Table l in which the percent by volume of the residual aromatics is given as a function of the operation time of the catalyst system.

TABLE I TABLE 1'] Time in a by volume of aromatics Yields b.w.

hours in the product The sulfur content of the product in this test has also been always lower than 0.3 ppm.

This example makes it apparent that the system of the invention is regenerable.

EXAMPLE 3 In this example the feedstock subjected to the treatment is kerosene and it is intended to improve its smoke point; for this purpose there iscarried out a par- I tial hydrogenation of the aromatic hydrocarbons contained therein.

'l'est (analytic /1 by volume of aromatics in numhcr system the final product after hours) H) 2U 4U bl) N0 l()() 150 200 220 l CATA. H 1.1, 2.5 5.4 2 CATA. HDS l 1.5 2.4 4.9

CATA. H 3 CATA. HDS A 05 0.5 05 05 05 0,6 1.5 2.4 4.5

CA'IA. H

I From the above table I it is apparent that only test No. 3 carried out according to this invention with the new catalysts results in the production, over a long period, of a product having the desired specifications by volume of aromatics 3). Moreover, the product is obtained during the whole test period with a yieldby weight close to 100% and with a sulfur content lower than 0.3 ppm by weight.

EXAMPLE 2 A test in every respect identical to test No. 3 of Example l is then carried out with the regenerated catalyst system; the obtained results are reported in the following table II:

The characterizing features of this kerosene are the following:

d 0.821 Sulfur content ppm by weight: 329 (in the form of sulfur compounds) Aromatics: 19% by volume (AFNOR MO 7 024) Smoke point: 18 mm (AFNOR M07 028) ASTM distillation: Initial point: 164C distilled point: 204.5C

Final point: 244.5C

It is desired to obtain a product having a smoke point higher than 23 mm, which corresponds approximatively to an aromatic hydrocarbon content smaller than 10% by volume.

The device used for carrying out this test is the following:' 1

The hydrodesulfurization catalyst also acting as H 5 absorbent is placed into two parallel reactors, one of which is in a regeneration phase while the other is in operation; the hydrogenation reactor is placed at the outlet of the operating hydrodesulfurization 'reactor' without using any intermediary fractionation device. The catalysts A.HDS.CATA. and

H.CATA. are identical to those described in example l. v The conditions of pressure, temperature and ratio of the hydrogen to the feedstock are the same for both operating reactors:

Total pressure: 55 Kg/cm Temperature: 300C H /feedstock: 1.5 in moles/mole. The p.p.h. values for the operating reactors are: A.HDS.CATA.: 1.35 (for l reactor in operation and the other in regeneration).

*7: by volume oi aromatic hydrocarbons in the product ufler (hours) 10 4O 80 l()() l50 I80 200 0.5 0.5 0.5 0.5 0.5 0.5 2.8 3.2

As above, there is obtained, over a long period, a product containing less than 3% by volume of aromatics, and with a yield close to 100% by weight and having a sulfur content lower than 1 ppm by weight.

What we claim as this invention is:

After 300 hours of continuous operation, the limit of the desired smoke point (23 mm) is reached, the first reactor containing the absorbing hydrodesulfurizing catalyst is then put in regeneration under a stream of steam as indicated in Example 2, while the second reactor containing the absorbing hydrodesulfurizing catalyst is put in operation until the smoke point limit is reached.

EXAMPLE 4 alumina and red muds with a ratio of the aluminaa to the red muds equal to 0.67 by weight. i The hydrogenation catalyst is the same as in the third test of example i. The operating conditions are in any respect identical to those of test No. 3 of example I. The obtained results are given in the following table:

7: by volume of aromatic hydrocarbons in the product after (hours) As in the test No. 3 of Example l there is obtained a product having the desired specifications over a long period, with a yield by weight close to 100% and a sulfur content lower than 0.5 ppm by weight.

EXAMPLE 5 There is carried out again a test identical to test No. 3 of example i, but using an absorbinghydrodesulfurizing catalyst based on nickel-tungsten.

The catalyst prepared as described in example l, from nickel nitrate and ammonium tungstate, contains 4.7% by weight of nickel oxide and 2i .8% by weight of tungsten oxide on a carrier of alumina and red muds with a ratio of the alumina to the red muds of 0.67 by weight.

As in example 4. the operating conditions and the hy= drogenation catalyst areunchanged.

The following results have been obtained:

H-C 8 l. A process for hydrogenating a feedstock of aro- The results obtained are given in table Ill below: matic compounds containing sulfur impurities in which TABLE III Operating 50 l()() 151i 200 320 240 2m 2x0 sou time in hours Smoke point 30 30 29 m5 :7 In 24.5 235 23 in mm ii by volume of (1.5 (L5 1.7 2.2 4.l .3 8.2 10.3 ll residual aromatics yields 71 h.\\'. 100 100.5

a mixture of hydrogen with at least one aromatic compound containing sulfur impurity is contacted, at a temperature of from 200 to 450C, under a pressure of from 10 to 200 kg/cm"; in successive order with:

A. A catalyst containing:

a. at least one desulfurizing element selected from the oxides and/or sulfides of molybdenum, tungsten, nickel and cobalt;

b. alumina and,

0. iron oxide, the ratio by weight of A1 0,, to Fe O in this catalyst being from 0.25 to 4; and,

B. A group Vlll metal hydrogenation catalyst.

2. A process according to claim 1, in which the desulfurizing element, calculated as metal, forms from 2 to 40% by weight of the catalyst A.

3. A process according to claim 1, in which the desulfurizing element is present in the form of a sulfide.

4. A process according to claim 1, in which the iron oxide is present in the form of red mud, which is a residue of the alumina manufacture.

5. A process accordingto claim 4, in which the red mud contains, by weight, from 30 to 60% of iron, ex pressed as Fe O from 1 to 10% of titanium, expressed as TiO from 5 to 20% of silicon, expressed as SiO from 5 to to l5% of sodium, expressed as Na co and from 5 to 30% of aluminum, expressed as A1 0 6. A process according to claim 1 in which the ratio of A1 0,, to Fe o in the catalyst (A) is from 0.65 to 1.8 by weight.

7. A process according to claim 1 in which the specific surface of the catalyst (A) is from 50 to 400 mlg.

8. A process according to claim 1, in which the specit 'ic surface of the catalyst (A) is from 100 to 300 m' /g.

9. A process according to claim 1, in which the catalyst contains from 5 to 35% by weight of molybdenum and/or tungsten oxide/or sulfide and from i to 10% by weight of nickel and/or cobalt oxide or sulfide, expressed as metal.

10. A process according to claim 1, in which the metal is platinum.

1 11. A process according to claim 1, in which the temperature is from 250' to 350C and the pressure from 20 to kg/cm.

12. A process according to claim I, in which the treated feedstock is a hydrocarbon fraction containing from 1 to by weight of aromatic hydrocarbons and from 1 to l000 ppm by weight of sulfur.

13. A process according to claim 1, further comprising regenerating the catalyst by passing steam through the catalysts A and B at a temperature from [00 to 600 C and thereafter employing the regenerated cata 11 r l2, lyst in the hydrogenation step. temperature of from 100 to 600C therethrough and 14. A process according to claim I further compristhereafter employing the regenerated catalyst in the hying regenerating the catalyst (A) by passing steam at a drogenation step. 

1. A PROCESS FOR HYDROGENATING A FEEDSTOCK OF AROMATIC COMPOUNDS CONTAINING SULFUR IMPURITIES IN WHICH A MIXTURE OF HYDROGEN WITH AT LEAST ONE AROMATIC COMPOUND CONTAINING SULFUR IMPURITY IS CONTACTED, AT A TEMPERATURE OF FROM 200* TO 450*C, UNDER A PRESSURE OF FROM 10 TO 200 KG/CM2, IN SUCCESSIVE ORDER WITH: A. A CATALYST CONTAINING: A. AT LEAST ONE DESULFURIZING ELEMENT SELECTED FROM THE OXIDES AND/OR SULFIDES OF MOLYBDENUM, TUNGSTEN, NICKEL AND COBALT, B. ALUMINA AND, C. IRON OXIDE, THE RATIO BY WEIGHT OF AI2O3 TO FE2O3 IN THIS CATALYST BEING FROM 0.25 TO 4, AND, B. A GROUP VIII METAL HYDROGENATION CATALYST.
 2. A process according to claim 1, in which the desulfurizing element, calculated as metal, forms from 2 to 40% by weight of the catalyst A.
 3. A process according to claim 1, in which the desulfurizing element is present in the form of a sulfide.
 4. A process according to claim 1, in which the iron oxide is present in the form of red mud, which is a residue of the alumina manufacture.
 5. A process according to claim 4, in which the red mud contains, by weight, from 30 to 60% of iron, expressed as Fe2O3, from 1 to 10% of titanium, expressed as TiO2, from 5 to 20% of silicon, expressed as SiO2, from 5 to to 15% of sodium, expressed as Na2CO3, and from 5 to 30% of aluminum, expressed as Al2O3.
 6. A process according to claim 1 in which the ratio of Al2O3 to Fe2O3 in the catalyst (A) is from 0.65 to 1.8 by weight.
 7. A process according to claim 1 in which the specific surface of the catalyst (A) is from 50 to 400 m2/g.
 8. A process according to claim 1, in which the specific surface of the catalyst (A) is from 100 to 300 m2/g.
 9. A process according to claim 1, in which the catalyst contains from 5 to 35% by weight of molybdenum and/or tungsten oxide/or sulfide and from 1 to 10% by weight of nickel and/or cobalt oxide or sulfide, expressed as metal.
 10. A process according to claim 1, in which the metal is platinum.
 11. A proCess according to claim 1, in which the temperature is from 250* to 350*C and the pressure from 20 to 70 kg/cm2.
 12. A process according to claim 1, in which the treated feedstock is a hydrocarbon fraction containing from 1 to 100% by weight of aromatic hydrocarbons and from 1 to 1000 ppm by weight of sulfur.
 13. A process according to claim 1, further comprising regenerating the catalyst by passing steam through the catalysts A and B at a temperature from 100* to 600*C and thereafter employing the regenerated catalyst in the hydrogenation step.
 14. A process according to claim 1 further comprising regenerating the catalyst (A) by passing steam at a temperature of from 100* to 600*C therethrough and thereafter employing the regenerated catalyst in the hydrogenation step. 